usb keypad

[theFob]

Hi,
I am very new to your forum and I wish to greet all of you.
I am hardware engineer and so I need a little help, when I am stick with software.
I have to made strange looking “usb” keyboard with big buttons, that will interact with “On Key what ever” event on regular PC. I will switch IP Cameras.
So in tree beers time I draw some hardware (attached below). I call this “kitchen made” prototype, because I will make him there. Well, I can buy numeric pad and put her in my grande buttons box (GBB) but this will not make me happy. It will be nice to choose char code for keys or even a string.
So I need help. After 2 hours googleing I have no answer on this – how to tell to PC, that this is standard keyboard?

I extend my board with LCD, RS232 and ICSP capability just in case. If someone find my board useful and if this someone lives in Europe, I can send him a board.